Mechanics

TOYOTA RAV4 SENSOR PROBLEM

1997 Toyota Rav4 • 14,950 miles

I have a Rav4 that has a stumble that is so hard that it is undrivable. It idles fine with no misses. The stumble happens mainly when the car has warmed up. Once the car warms up it stumble over and over repeatedly.
The car has no codes set.
It did have a trans shifting problem that turned out to be a throttle position sensor issue. The sensor itself was OK, it was the plug that caused the problem. The plug was cleaned and the trans down shifted fine after that.
So I'm not sure if this sensor could be the problem again or not.

Thanks for any help you can give me.
Avatar
Guest
November 27, 2012.



A TPS fault would usually show trouble codes and if you have a scan tool, you should be able to monitor/test the TPS voltages. A faulty TPS would usually show as lack of power or poor response but not jerking.

Severe misfiring symptoms are usually ignition sparks related and the most likely cause would be the ignition coil.


KHLow2008
Nov 27, 2012.
The tab that holds the coil wire onto the coil had broken off, so I replaced the coil. But that didn't solve the problem.
When the car stumbles, the engine light comes on and goes right back off. And no codes are stored.
The only major problem this car had was with the trans, and it was rebuilt
about a year ago.

I'm not sure where to go from here. Wires, cap, and plugs?

Thanks


Tiny
Sixgunn
Dec 3, 2012.
Have the coil and spark plug wires ohmed out. They must have continuity and resistance below 25k ohms, preferably below 15 k ohms.

Have you checkd the spark plugs?


KHLow2008
Dec 3, 2012.
I'll check the plugs and wires tomorrow. The coil is new, so it should be good to to go.


Tiny
Sixgunn
Dec 4, 2012.
The plugs look good, and are fairly new (NGK's). And the wires all test under 15K.


Tiny
Sixgunn
Dec 7, 2012.
Wires must have continuity.
Ensure all connections of spark plug and coil wires are tight and secure.

The MIL coming on and going off is a bit strange. Usually when it comes on, it should stay on until the ignition is turned off. This could mean a fault with ground circuits or a fault with the PCM or ignition switch/power supply.

Being intermittent and not throwing any codes indicates a problem that is never easy to diagnose. The next time the problem occurs when the MIL flashes, get a scan done without turning the ignition off and see if you can come up with anything.


KHLow2008
Dec 7, 2012.
When you mentioned a fault with ground circuits I remembered that I had taken a wire off the neg. Side of the battery. This wire was fished through the firewall and was hooked to the battery. I thought the wire was unimportant because it was obviously not original to the car. And I thought it was for a radio or something like that the previous owner had done. I grounded this wire to the body and the car no longer stumbles. This "home made wire" concerns me but the stumbling problem is gone.

This Rav has developed a different problem now, so I'm going to start a new question.

Thanks for the great help.


Tiny
Sixgunn
Feb 4, 2013.
You're welcome and glad to know you have solved the problem.


KHLow2008
Feb 4, 2013.
Hello KHLow2008, I wondered if you could take the time to look at the issues I'm have with this '97 Rav4 now. I did post the question listed below as a separate question, and donated money with this question, but no one had an answer so far on this problem. My daughter has stopped driving the car because it's costing her to much in gas to drive it. Thanks

My daughter's 1997 Rav4 has set two codes PO133 and PO401. For the EGR code I bought a used EGR at a junkyard and the code stayed off for a few days and came back. The engine has developed a poor idle during a stop. This happens only sometimes, but when it does idle poorly it will come close to stalling. When accelerating the engine feels underpowered.
I checked the timing, and it is around 15 degrees. It should be 10 according to the manual. The distributor in this car is un-adjustable.
The worst part of the way the car is running is the gas mileage. It's getting about 160 miles to a tank of gas, and that's on a good day. The car should get around 19-21 mpg (all wheel drive).
Any help you can give me would be great. I know my daughter is to the point where she can't afford to drive the car.


Tiny
Sixgunn
Feb 7, 2013.
Lets start with the P0401, which could be the cause of the O2 sensor fault or it could be 2 problems but definitely both are affecting the mileage and performance.

1. Check all EGR system vacuum hoses. Replace as necessary. Access ECM behind bottom center of instrument panel, in front of console. Ensure ignition is off. Disconnect ECM E4 connector. Turn ignition on. Connect a jumper wire between ground and terminal No. 23 (Black/White wire) at ECM E4 connector.

2. With jumper wire connected, Vacuum Switching Valve (VSV) is on. Apply air pressure to VSV port "E". Air from port "E" should flow through filter on end of valve. See Fig. 4. Disconnect jumper wire. Air from port "E" should flow from port "G". If valve operates as specified, go to step 6). If valve does not operate as specified, go to next step.

3. Turn ignition off. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 33-39 ohms at 68°F (20°C). Check for continuity between each terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.

4. Check VSV operation. Apply battery voltage to valve terminals. Apply air pressure to VSV port "E". Air from port "E" should flow from small filter on end of valve. See Fig. 4. Remove battery voltage from valve terminals. Air from port "E" should flow from port "G". Replace VSV as necessary.

5. Check for an open or short in wiring harness between instrument panel fuse block and ECM. Repair wiring as necessary.

6. Check EGR vacuum modulator. Replace as necessary. If EGR vacuum modulator is okay, check EGR valve. Replace as necessary. If EGR valve is okay, go to next step.

7. Check Manifold Absolute Pressure (MAP) sensor. Replace MAP sensor as necessary. If MAP sensor is okay, replace ECM and retest.


KHLow2008
Feb 7, 2013.